Stacks of electric devices are known. In order to test a stack, permanent electric connections (e.g. solder connections) are formed between the devices after having stacked them above each other. Then, the stack is tested as a whole by applying electric testing signals to the stack. One disadvantage is that usually the stack as a whole has to be discarded if it does not work as intended, even if the single electric devices work correctly. Since it is often not possible to re-separate the electric components from each other, the production yield may be relatively low.